Amphibology

An amphibology is a sentence or phrase that has two (or more) different meanings, but it's not clear which one is meant. It's like when someone says something and you don't understand what they mean. For example, if someone said, "The band are playing at noon," you wouldn't know if they meant that the band is playing music at noon or that the members of the band are meeting at noon. That's an amphibology!